Trucks, particularly tank trucks, are widely used for transporting a multitude of different liquids. Since liquids typically have relatively high densities and are carried in large volumes, considerable load weights are involved in their transportation. For example, in the case of tank trucks carrying loads as small as 1500 gallons, modest by todays standards, and assuming a liquid density of about 8.3 pounds per gallon, the value for water, a load weight of about 6 tons is involved. Tank trucks traveling todays highways, do so at relatively high speeds; consequently, the momentum of such loads, i.e., the product of the load's mass times its velocity, can be extremely high. When it becomes necessary to stop the vehicle abruptly, for instance, in an emergency, the inertial forces created by the sudden shifting of the load can have a serious destabilizing effect on the vehicle. Such destabilization tends to cause loss of control of the vehicle, with attendent risks of damage to the vehicle and its load, as well as serious injury to the driver and those otherwise involved in the incident.
To avoid such destabilization the tank can of course be filled to capacity; however, it is not always possible or desirable to carry full loads. An alternative expedient involves the installation of baffles in the interior of the tank positioned at right angles to the anticipated movement of the vehicle carrying it. Such baffles, in effect, form compartments within the tank, limiting the distance that the tanks cargo can shift, thus minimizing the build-up of liquid velocities, and thereby ameliorating the destabilizing effects that would otherwise occur. The number of baffles required, and the nature of their structure, depends upon the length of the tank in which they are incorporated, the density of the liquid being carried, the anticipated operating speeds of the vehicle, and similar considerations. In order to be able to successfully resist the forces involved, it is frequently necessary to either have a large number of baffles mounted within the tank, or to design baffles with structural elements of substantial strength. The problem described is particularly acute in the case of tanker trucks used for carrying water to fires in rural areas where water supply from hydrants is not available. Fire tanker trucks used for carrying water commonly do so by drawing water supplies into the tank by vacuum, and then rushing to the scene of the fire where the water is unloaded into a temporary structure, the truck thereafter returning for additional water. In such service, the truck is operated at high speeds, frequently over uneven terrain, and with partial loads, frequent sudden braking being the rule, rather than the exception. Since the tanks carried by such trucks are normally not completely filled, sudden surges of the water held therein are common. The problem is so severe that the National Fire Provention Association states that some individuals consider the age-old problem associated with tank "baffles" or "swash partitions" as the weakest and most dangerous area of fire engine and tanker design and construction. While indicating that considerable improvements have been made in baffles since the advent of the computer age, the NFPA states that poor baffling has been responsible for many accidents, and each year is accountable for a number of deaths over the country. It suggests, therefore, that careful consideration be given to baffles by the designers and builders of the tanks.